1. Field of the Invention
The invention relates to a chair construction, more particularly to a chair with a seat and backrest that can be retained adjustably at desired inclined positions.
2. Background of the Invention
Referring to FIGS. 1 and 2, a conventional chair is shown to comprise an upright pneumatic cylinder (C) mounted on a mobile base (B), a platform (D) mounted on a top end of the pneumatic cylinder (C), a seat support (E) mounted pivotally on the platform (D), a base plate (F) secured to the seat support (E), a seat (G) fixed to the base plate (F), and a backrest (H) mounted pivotally on a rear end of the base plate (F).
The top end of the pneumatic cylinder (C) is provided with a control knob (C1). A control lever (I) is mounted pivotally on the platform (D) and is operable so as to actuate the control knob (C1) in order to vary the length of the pneumatic cylinder (C) and adjust the height of the chair. A spring (J), a bolt (J1) and a control knob (J2) are disposed between the front ends of the platform (D) and the seat support (E) and permit limited pivoting movement of the seat support (E) and the seat (G) relative to the platform (D). A connecting seat (K1), a connecting plate (K2), a pair of springs (K3) and a mounting plate (K4) are provided between the base plate (F) and the backrest (H) and connect resiliently the same so as to permit inclination of the backrest (H) relative to the base plate (F) and the seat (G). A positioning tube (H1) is welded to a lower end of the backrest (H). A slide seat (L1) is provided on the base plate (F) and permits the passage of a slidable positioning rod (L) therethrough. When the positioning rod (L) extends into the positioning tube (Hi), the backrest (H) is prevented from inclining rearwardly relative to the base plate (F). Inclining movement of the backrest (H) is permitted only when the positioning rod (L) ceases to extend into the positioning tube (H1).
The drawbacks of the above described conventional chair are as follows:
1. The backrest (H) can be retained in an upright position only. Retaining of the backrest (H) at a desired inclined position is not permitted. PA1 2. Since the conventional chair includes a large number of small components, the manufacture and assembly of the conventional chair is relatively complicated and entails a high manufacturing cost. PA1 3. The restoration force for restoring the backrest (H) to the upright position cannot be adjusted to suit the user's requirements. For example, if the spring force of the springs (K3) is relatively strong, a small child would have difficulty in forcing the backrest (H) to the desired inclined position. PA1 4. Although limited pivoting movement of the seat (G) is permitted, retaining of the seat (G) in an inclined position is also not permitted.